Living Radical Polymerization: RAFT/ATRP vs Conventional (2D)

Mechanism

Kinetics

Propagation rate k_p[M] 1.2

Deactivation frequency k_deact 1.0

Simulation speed 1.0×

Live Readouts

M_n (number-avg DP)

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M_w (weight-avg DP)

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Dispersity Đ = M_w/M_n

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Conversion

Active chains

0 / 36

Active (growing) Dormant Terminated

Top panel: drag to pan, scroll/pinch to zoom the 36-chain grid. Hover a column to inspect it.

How it works

Each of 36 chains is tracked individually as it grows one monomer unit at a time, exactly as in reversible-deactivation radical polymerization (RDRP) — the mechanism behind ATRP and RAFT. This 2D view draws every chain as a rising bead column so growth, state and final length are all readable at a glance, plus a live length histogram and a dispersity/conversion strip-chart.

Living / RDRP mode: a chain flips rapidly between active (adds monomer, rate k_p[M]) and dormant (frozen, no radical) states. Because every chain visits the active state only briefly and equally often, all chains grow at nearly the same average rate:

Đ ≈ 1 + (k_p[M]) / (k_deact · DP_n)

Faster deactivation (higher k_deact) means shorter active bursts, so chain lengths stay close together and Đ → 1.

Conventional free-radical mode: chains initiate at random times throughout the reaction (not all at once), grow continuously once active, and are permanently destroyed by radical–radical termination. Chains born early grow long before they die; chains born late stay short. The result is the classical Flory "most probable" distribution:

Đ = M_w/M_n = 1 + p   (p = conversion, → 2 at high conversion)

This is exactly why RAFT/ATRP revolutionised polymer synthesis in the 1990s: the same monomer and similar conversion give Đ ≈ 1.05–1.3 instead of Đ ≈ 1.5–2.0, enabling precision block-copolymer engineering. Both closed-form ratios above are the standard textbook results for RDRP and Flory's most-probable distribution respectively — verified consistent with the discrete per-tick simulation below.

36-chain grid

Length distribution

Đ & conversion vs time

Living Radical Polymerization: RAFT/ATRP vs Conventional Free-Radical (2D)